Waka Kotahi has escaped prosecution over the deaths of several kororā (little blue penguins) at one of its construction sites in Wellington.
An investigation concluded the NZ Transport Agency was responsible for only one death.
The agency has since been slapped with a warning but some wildlife advocates have said that's not enough.
Waka Kotahi's cycleway construction site near Pito-one/Petone is where several kororā were found dead earlier this year.
"The death of any protected wildlife is tragic," said Matt Davis, principal investigator at Te Papa Atawhai/Department of Conservation (DoC).
"Because the penguin was killed with a rock being moved, it did fall under the Wildlife Act and we took action accordingly," Davis told Newshub.
That action was to hand down Waka Kotahi and the developers a formal warning.
"It's not a fine, it's not a prosecution, however, should any further deaths of penguins occur then the warning would be taken into account," Davis said.
But it's not enough action for one wildlife advocate.
"They've just been given a license to continue doing what they're doing - a formal warning is hardly a deterrent," said Amelia Geary, spokesperson for Te Reo o te Taiao/Forest & Bird.
Waka Kotahi declined Newshub's request for an interview but said in a statement it fully accepts the investigation's findings.
The agency said substantial changes have been made since and no further deaths have occurred.
"I have seen the measures they've put in place and it's my opinion they've gone above and beyond what's reasonable," said Davis.
Measures that one penguin expert hopes are sufficient.
"Every penguin that dies didn't need to - that's one less bird in the breeding population and one less bird to contribute to the survival of the species," said John Cockrem from Massey University.
